1. Field of the Invention
The present invention relates to a canister for volatile fuel controlling device in an internal combustion engine.
2. Description of the Prior Art
A volatile fuel controlling device is well known in which the volatile fuel generated from a fuel tank, fuel reservoir of a float chamber in a carburetor and the like is gathered by a canister without being exhausted in the atmosphere and thus gathered volatile fuel is drawn from the canister in association with the operation of the engine for combustion purposes. Recently the permissible levels of volatile fuel emissions in the atmosphere have been severely restricted and therefore it is required to properly control the emission of volatile fuel from the volatile fuel controlling system.
As a countermeasure of the above-mentioned problem, it has been suggested to increase the amount of absorbent such as activated carbon filled inside of the canister, by which a large amount of volatile fuel is caught so as to prevent the emission thereof into the external air. This idea is disadvantageous, however, in that the canister becomes inevitably of large size, which results in an increase of manufacturing cost and a difficulty of mounting it in a small-sized vehicle.
Another countermeasure has also been suggested such that the scavenging effect of the canister is increased so that a large amount of volatile fuel can be caught by a relatively small amount of absorbent filled inside of the canister. This method is indeed advantageous in that an increase in the amount of scavenged air in the canister insures a control of a large amount of volatile fuel with only a small amount of absorbent. However, this method also has problems because it causes a decrease of the engine feeling and affects the density of air-fuel mixture, which results in an increase of the amount of unburned component remaining within the exhaust gas.